The present invention relates to a system for treating vascular disease. More specifically, the present invention relates to a system for deploying a stent in a bifurcation lesion.
Vascular disease currently represents a prevalent medical condition. Typical vascular disease involves the development of a stenosis in the vasculature. The particular vessel containing the stenosis can be completely blocked (or occluded) or it can simply be narrowed (or restricted). In either case, restriction of the vessel caused by the stenotic lesion results in many well known problems caused by the reduction or cessation of blood circulation through the restricted vessel.
A bifurcation is an area of the vasculature where a first (or parent) vessel is bifurcated into two or more branch vessels. It is not uncommon for stenotic lesions to form in such bifurcations. The stenotic lesions can affect only one of the vessels (i.e., either of the branch vessels or the parent vessel) two of the vessels, or all three vessels.
Vascular stents are also currently well known. Vascular stents typically involve a tubular stent which is movable from a collapsed, low profile, delivery position to an expanded, deployed position. The stent is typically delivered using a stent delivery device, such as a stent delivery catheter. In one common technique, the stent is crimped down to its delivery position over an expandable element, such as a stent deployment balloon. The stent is then advanced using the catheter attached to the stent deployment balloon to the lesion site under any suitable, commonly known visualization technique. The balloon is then expanded to drive the stent from its delivery position to its deployed position in which the outer periphery of the stent frictionally engages the inner periphery of the lumen. In some instances, the lumen is predilated using a conventional dilatation catheter, and then the stent is deployed to maintain the vessel in an unoccluded, and unrestricted position.
Self-expanding stents can also be used. Self-expanding stents are typically formed of a resilient material. The resilient material has sufficient resilience that it can be collapsed to the low profile position and inserted within a delivery device, such as a catheter. Once the catheter is placed at the site of the stenotic lesion, the stent is pushed from within the catheter such that it is no longer constrained in its low profile position. The stent, driven by the resilience of the material, expands to a higher profile, deployed position in which its outer periphery frictionally engages the walls of the stenosed vessel, thereby reducing the restriction in the vessel.
While there have recently been considerable advances in stent design and stent deployment techniques, current methods of treating bifurcation lesions are suboptimal, particularly where both downstream branch vessels are affected by the lesion. Current techniques of dealing with such lesions typically require the deployment of a slotted tube stent across the bifurcation. However, this compromises the ostium of the unstented branch.
Further, once the first stent is deployed, the treating physician must then advance a dilatation balloon between the struts of the stent already deployed in order to dilate the second branch vessel. The physician may then attempt to maneuver a second stent through the struts of the stent already deployed, into the second branch vessel for deployment. This presents significant difficulties. For example, dilating between the struts of the stent already deployed tends to distort that stent. Further, deploying the second stent through the struts of the first stent is not only difficult, but it can also distort the first stent. Thus, the current systems used to alternately deploy stents in a bifurcated lesion have significant disadvantages.
Also, since two guidewires are often used to deploy stents at a bifurcation, the guidewires can become crossed, or somewhat entangled. The deployment systems which are advanced along such guidewires can become caught on the wires, where they cross over one another. This can require additional time and manipulation of the stent deployment system in order to properly deploy the stent at the bifurcation.
Further, some branch vessels can have somewhat smaller diameter lumens than the parent vessels from which they branch. Therefore, stents of different sizes need to be deployed in the parent vessel and the branch vessel. Alternatively, a single stent having a larger diameter portion, and one or more smaller diameter portions, can be deployed at the bifurcation. However, this can lead to difficulty in deployment. For instance, a balloon which is sized to fit within the smaller diameter stent portion, and deploy that portion, may not be large enough to deploy the larger diameter stent portion. Therefore, a plurality of balloon catheters must be used to deploy such stents.